How to detect scene strips in the VSE on frame changes?
This works, but I guess it could be more elegant and faster if ".strip_elem_from_frame" would work with scene-strips and nonactive strips. The current strip will be written in the Console. 

import bpy

#update at frame change
def syncSceneLength(*pArgs):
    scn = bpy.context.scene
    seq = scn.sequence_editor
    cf = scn.frame_current
    for i in seq.sequences:    
        try:
            if (i.frame_final_start &lt;= cf
            and i.frame_final_end &gt; cf
            and not i.mute): 
                print("Current Strip: "+i.name)
        except AttributeError:
                pass

def attachAsHandler():
    for f in bpy.app.handlers.frame_change_pre:
        bpy.app.handlers.frame_change_pre.remove(f)
    bpy.app.handlers.frame_change_pre.append(syncSceneLength)

def detachAsHandler():
    bpy.app.handlers.frame_change_pre.clear()    

syncSceneLength()
attachAsHandler()
#detachAsHandler() #Uncomment this to stop handler